Ahoy Maties! Welcome Liveaboards, I know it's a funny subject but deserves much consideration. I have found a great discussion in a forum that I found extremely helpful in my toilet buying decision. They discuss models, installs etc.
Here is what I gained from reading in the forum:
It appears that many people still prefer the old pump models because of ease of maintenance reasons. Some even spoke of the old plank with a hole in it hanging over the bow (I wouldn't recommend that model :) ). It looks as though the most reliable toilet they speak of is the Sealand Traveler. Ease of install and performance also wins it some praise.Sealand is known to be one of the most costly of the marine toilets, but many would say, well worth the price!
Some believe that the easiest install, and needing less pumpouts is the Sealand RV style toilet which has it's holding tank directly below which causes it to use much less water.
Here are two other models that got Kudos for sailboats: Crittenden Skipper for normal sized sailboats, Groco Model K-H, and groko.There was also some discussion on composting toilets but that didn't make it to far. I think we can all see the problems there....
There are still those that believe that the old "Bucket and Chuck it" is the way to go but I think I will be looking into a vaccu flush for myself :)
Have a great day living aboard your boat!